JP3047724B2 - X-ray mask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray mask, and more particularly to an X-ray mask arranged as a dummy mask between a light source for generating X-rays of an X-ray exposure apparatus and an object to be exposed.

[0002]

BACKGROUND ART Photolithography technology is indispensable for manufacturing semiconductor devices such as ICs, LSIs, and VLSIs. With the increase in integration of ICs and the like and miniaturization of elements such as transistors, the rules for forming wiring films and the like have been changed from 1 μm to 0.5 μm.
From 0.5 μm to 0.3 or 0.2 μm. Accordingly, the wavelength of the light beam used for exposing the resist film must be shortened. In particular, 0.
To realize the 3 or 0.2 μm rule, it is necessary to use X-rays as exposure light beams. FIG. 6 is a perspective view schematically showing the configuration of an X-ray exposure apparatus used for X-ray lithography.

[0003] In the drawings, reference numeral 1 denotes an electron storage ring for circulating electrons incident from an incident system (not shown). The electrons are tangentially SOR when bent by a magnetic field
(Syn-chrotron Radiation) 2 is emitted. Reference numeral 3 denotes a vibrating mirror, which rotates while reflecting the SOR2, thereby
The scan of OR2 is performed. 4 is a helium chamber, 5
Reference numeral 5 denotes a Be window provided in the helium chamber 4, through which the SOR 2 passes. Reference numeral 6 denotes an exposure mask, and reference numeral 7 denotes a semiconductor wafer to be exposed. FIG. 7 is a sectional view showing an exposure mask and a semiconductor wafer.

The exposure mask 6 is made of a light transmitting material 8 made of SiN.
The light absorbing film 9 made of, for example, tantalum carburite is patterned on the surface of the substrate. Reference numeral 10 denotes a support frame formed on the surface of the light transmitting material 8 on the side opposite to the light absorbing film. Semiconductor wafer 7
Has a resist film 11 formed on its surface, and the surface on which the resist film is formed faces the exposure mask 6. The principle of the SOR light source is described in, for example, IEEE Japan, Vol. 108
-D, No. 9, '88, pp. 792-796.

[0005]

FIGS. 6 and 7 show an embodiment of the present invention.
According to the conventional example shown in (1), during exposure, there is a risk that the exposure mask absorbs a part of the X-rays and raises the temperature, thereby causing thermal deformation. This will be described in detail below. The light beam that I really want as the exposure light beam has a wavelength λ of 1
Although it is of the order of 0 Angstroms, in practice, those having a longer wavelength, specifically those having a wavelength of 20 to 30 Angstroms, are also included in the exposure light beam. On the other hand, the light transmitting material 8 made of SiN, which is the base of the exposure mask 6, has a light transmitting characteristic as shown in FIG. 8 and has a light transmittance of about 80% for light having a wavelength λ of 10 Å. However, the light transmittance becomes lower than 80% for light having a longer wavelength, and the light transmittance becomes 0 for light having a wavelength λ of 20 Å or more.
%.

That is, a part of the X-ray from the light source is absorbed even in the portion of the exposure mask 6 where the light absorbing film 9 is not formed. Then, the absorbed light turns into heat to raise the temperature of the exposure mask 6, which causes the exposure mask 6 to be thermally deformed. The thermal deformation of the exposure mask 6 is not preferable because it lowers the lithography accuracy. Therefore, the present inventor has devised to dispose a dummy mask made of a light transmitting material on the light source side of the exposure mask 6. With this configuration, the X-rays absorbed by the light transmitting material of the exposure mask can be absorbed by the dummy mask, so that the amount of X-ray absorption by the light transmitting material of the exposure mask can be reduced.
Eventually, the temperature rise of the exposure mask can be reduced to reduce the thermal deformation. An X-ray exposure apparatus in which a dummy mask made of a light transmitting material is arranged on the light source side of the exposure mask has already been proposed by the present applicant in Japanese Utility Model Application No. 1-48697.

However, the exposure mask is made of a light transmitting material, and as shown in FIG. 8, the light transmitting material absorbs part of energy but transmits most of energy. The amount of energy required for exposure is increasing to meet the demand for improvement in throughput, and is expected to be ten times or more in the near future. Therefore, there is a possibility that thermal deformation of the exposure mask cannot be reliably prevented only by arranging the dummy mask composed of only the light transmitting material on the light source side of the exposure mask.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and more effectively prevents the exposure mask from absorbing X-rays at the time of exposure and increasing the temperature to thereby thermally deform the mask. The purpose is to:

[0009]

An X-ray mask according to claim 1 overlaps at least a part of a mask pattern of the exposure mask with a surface of a dummy mask made of a light transmitting material provided on a light source side of the exposure mask. A light absorbing film having a pattern that does not overlap with a part where no pattern is formed is provided.

[0010]

According to the X-ray mask of the present invention, since the X-rays are absorbed by the light absorbing film provided on the surface of the light transmitting material of the dummy mask, the amount of X-ray absorption by the exposure mask is reduced accordingly.
Temperature rise is suppressed. Therefore, thermal deformation of the exposure mask can be more effectively prevented.

Then, a shape is formed on the light transmitting material surface of the dummy mask.
The formed light absorbing film overlaps the mask pattern of the exposure mask
Because it has a pattern, the light transmission material surface of the dummy mask
The X-ray exposure pattern may be affected by the light absorbing film
Not at all.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to 3 show the X-ray mask of the present invention.
Illustrates one embodiment, FIG. 1 is a perspective view showing a configuration of an X-ray exposure apparatus using the present invention X-ray mask as a dummy mask, FIG. 2 and the dummy mask, an exposure mask, the object to be exposed FIG. 3 shows a dummy mask, an exposure mask,
FIG. 3 is a perspective view showing an object to be exposed. X shown in FIGS. 1 to 3
The linear exposure apparatus differs from the X-ray exposure apparatus shown in FIGS. 6 and 7 in that a dummy mask is provided, but is otherwise the same, and the common points are the same. 6, the same reference numerals as those used in FIG. 7 are assigned and shown, and the description is omitted, and only different points will be described.

Reference numeral 12 denotes a dummy mask as a first embodiment of the X-ray mask of the present invention, which is disposed on the light source side of the exposure mask 6 and has the same material as the light transmitting material which is the base of the exposure mask 6.
For example, a substrate is made of SiN, and light absorbing films 14, 14,... Made of, for example, tantalum carbide are selectively formed on the surface thereof. Reference numeral 10 denotes a support frame. The light absorbing films 14, 14,... Are formed in a pattern that does not protrude from the light absorbing films 9, 9,. This is to prevent the pattern to be exposed from being affected by the presence of the light absorbing films 14, 14,.... More specifically, the exposure mask 6 is formed to have a width smaller than that of the light absorption film 9 of the scribe line corresponding to the scribe line. The pattern drawn in each area surrounded by the scribe lines of the exposure mask 6, that is, in the semiconductor element (chip) area has a very complicated shape, but is simply L-shaped for convenience in the drawings.

In the present X-ray exposure apparatus, since the dummy mask 12 made of the same material as the light transmitting material 8 of the exposure mask 6 is arranged on the light source side of the exposure mask 6, if the dummy mask 1
If there is no X-ray, the X-rays absorbed by the light transmitting material 8 of the exposure mask 6 are considerably absorbed by the dummy mask 12. The wavelength .lambda.
The light is only about angstrom or less. Light having a wavelength λ of 10 Å or less reaching the exposure mask 7 passes through the light transmitting material 8 of the exposure mask 6 and is incident on the resist film 11 on the surface of the semiconductor wafer 7 except for the light incident on the light absorbing film 9. I do.

The light absorbing films 9, 9,.
Most of the X-rays that should have been absorbed by the light absorption films 9 corresponding to the scribe lines,
4, 14, ... are absorbed. Accordingly, the amount of light absorbed by the exposure mask 6 is very small, and the temperature rise of the exposure mask 6 is also small. Accordingly, there is no possibility that the exposure mask 6 is thermally deformed. Although the dummy mask of the present embodiment was formed of the same material as the light transmitting material of the exposure mask, it is not always necessary to do so. What is necessary is just to have the filter characteristic which does not cut light.

FIG. 4 is a plan view showing another example of the exposure mask of the X-ray exposure apparatus. In the figure, reference numeral 8 denotes a light transmitting material made of SiN as an exposure mask, and reference numeral 15 denotes one mask pattern formed on the surface of the light transmitting material 8. The mask pattern 15 is formed by assembling island-shaped fine light absorbing films (made of, for example, tantalum carbide) 16, 16,... . The size of the gaps 17, 17,... Is, for example, 0.1 μm or less, which is small enough not to be transferred from X-ray diffraction. The length (width) of one side of the fine island-shaped light absorbing film 17 is, for example, about 0.5 to 0.25 μm.

In this manner, the mask pattern 15 is formed by grouping the island-shaped fine light absorbing films 16, 16,... Independent from each other with small gaps 17, 17,. When the temperature of the exposure mask rises and the light absorbing film expands, the expansion of the light absorbing film is absorbed by the gaps 17, 17,..., And a strong stress is generated between the light absorbing film and the light transmitting material as the substrate. Can not be. That is, conventionally, each mask pattern of the exposure mask is formed by the integral light absorbing film 15 as shown in FIG. Therefore, when the temperature of the exposure mask rises due to absorption of X-rays, a large stress is generated between the light absorbing film 15 and the light transmitting material 8 as a substrate due to thermal expansion. This is unavoidable because the light transmitting material as the substrate is extremely thin, a few μm, and the diameter or width of the exposure area is as wide as about 20 mm.

However, the problem can be solved by forming the pattern as a group of independent fine light absorbing films in an island shape with fine gaps as in the present exposure mask. Needless to say, a dummy mask 12 may be further provided on the light source side of the main exposure mask 6.

[0019]

According to the first aspect of the present invention, there is provided an X-ray mask in which a mask pattern made of a light absorbing film is formed on a surface of a light transmitting material which is disposed between a light source for generating X-rays and an object to be exposed. An X-ray mask arranged as a dummy mask on the light source side of the mask, wherein at least a part of the light absorbing film of the exposure mask on the surface of the light transmitting material overlaps with a part where the light absorbing film is not formed. It is characterized in that a light absorbing film is formed at a position where it does not overlap. Therefore, according to the X-ray mask of the first aspect, since the X-rays are absorbed by the light absorbing film provided on the surface of the light transmitting material of the dummy mask, the amount of X-ray absorption by the exposure mask is reduced, and the temperature rises. Is suppressed. Therefore, thermal deformation of the exposure mask can be more effectively prevented. Since the light absorbing film formed on the light transmitting material surface of the dummy mask has a pattern overlapping the mask pattern of the exposure mask, the X-ray exposure pattern may be affected by the light absorbing film on the light transmitting material surface of the dummy mask. Not at all.

[Brief description of the drawings]

FIG. 1 is a perspective view of an X-ray exposure apparatus for explaining one embodiment of an X-ray mask of the present invention.

FIG. 2 shows a dummy mask for explaining the embodiment,
FIG. 3 is a cross-sectional view of an exposure mask and an object to be exposed.

FIG. 3 shows a dummy mask for explaining the embodiment,
FIG. 3 is a perspective view of an exposure mask and an object to be exposed.

FIG. 4 is a plan view of another embodiment of the X-ray mask used in the X-ray exposure apparatus .

FIG. 5 is a plan view of a conventional example of an X-ray mask compared with the X-ray mask of FIG. 4;

FIG. 6 is a perspective view of an X-ray exposure apparatus for explaining background art.

FIG. 7 is a cross-sectional view of an exposure mask and an object to be exposed for explaining background art.

FIG. 8 is a light transmission characteristic diagram of a light transmission material for describing a problem to be solved by the invention.

[Explanation of symbols]

 Reference Signs List 6 X-ray mask (exposure mask) 8 Light transmitting material 9 Light absorbing film 12 X-ray mask (dummy mask) 13 Light transmitting material 14 Light absorbing film

Claims (1)

(57) [Claims] 1. A dummy mask is disposed on a light source side of an exposure mask in which a mask pattern formed of a light absorbing film is formed on the surface of a light transmitting material which is disposed between a light source for generating X-rays and an object to be exposed. An X-ray mask, wherein a light-absorbing film is formed at a position on the surface of the light-transmitting material that overlaps at least a part of the light-absorbing film of the exposure mask and does not overlap with a portion where the light-absorbing film is not formed. X-ray mask characterized by becoming